The present invention relates generally to the production of bent, tempered sheets of glass and, more particularly, to a transfer apparatus for reorienting a glass sheet from a horizontal plane to a substantially vertical plane for optimum processing.
Generally, the commercial production of bent, tempered glass sheets, such as are utilized as glazing closures for automobiles and the like, includes heating the sheets to the softening point of the glass, bending the heated sheets to the desired curvature and thereafter chilling the sheets in a controlled manner to a temperature below the annealing range of the glass.
One successful method for producing such sheets in large quantities involves carrying out these steps continuously in a mass production, horizontal line operation whereby the sheets are supported in a horizontal plane and advanced on externally driven conveyor roll-type conveyors in a horizontal path successively through a heating area, a bending area and a heat treating or chilling area for tempering the bent sheets. In a horizontal production line such as described above, the tempering is usually effected by directing opposed streams of cooling fluid, such as air or the like, toward and against the opposite surfaces of the sheet as they are advanced in the aforementioned horizontal path.
While this horizontal production line glass bending and tempering operation has proven to be highly successful and admirably suited for the production of automotive glass sheets of conventional thicknesses, say about 0.125 inch and thicker for example, problems are encountered in commercially processing thinner glass sheets by this procedure. For example, the air tempering of glass sheets having thicknesses less than 0.125 inch sometimes creates optical and surface defects in the glass surfaces because of the pitting or dimpling effect caused by the air streams impinging against the opposite surfaces of the thin heat-softened sheets. Moreover, the tremendous power requirements necessary to generate the necessary pressure and volume to effect proper tempering of such thin sheets, if attainable, and which is completely dissipated into the atmosphere, add materially to production costs.
Various attempts have been made to overcome this problem in the horizontal processing of thin tempered glass sheets, i.e. sheets having thicknesses ranging from about 0.090 to 0.125 inch for example. One such effort involved the use of a different cooling medium, such as a liquid bath, for example. However, it was found virtually impossible to uniformly cool the opposite surfaces of the sheets at the same cooling rate when employing a liquid medium adapted to receive horizontally oriented sheets in a continuous horizontal production line operation.